This quickstart will get you going with Java and the Jetty embedded web server on the Cedar stack.
Sample code is available on github along with this document. Edits and enhancements are welcome. Just fork the repository, make your changes and send us a pull request.
- Basic Java knowledge, including an installed version of the JVM and Maven 3.
- Your application must run on the OpenJDK version 6.
- A Heroku user account. Signup is free and instant.
We'll start by setting up your local workstation with the Heroku command-line client and the Git revision control system; and then logging into Heroku to upload your ssh public key. If you've used Heroku before and already have a working local setup, skip to the next section.
| If you have... | Install with... |
|---|---|
| Mac OS X | Download OS X package |
| Windows | Download Windows .exe installer |
| Ubuntu Linux | apt-get repository |
| Other | Tarball (add contents to your $PATH) |
Once installed, you'll have access to the heroku command from your command shell. Log in using the email address and password you used when creating your Heroku account:
:::term
$ heroku login
Enter your Heroku credentials.
Email: adam@example.com
Password:
Could not find an existing public key.
Would you like to generate one? [Yn]
Generating new SSH public key.
Uploading ssh public key /Users/adam/.ssh/id_rsa.pub
Press enter at the prompt to upload your existing ssh key or create a new one, used for pushing code later on.
You can run any Java application on Heroku that uses Maven as build tool. As an example, we will write a web app using Jetty. Here is a basic servlet class that also contains a main method to start up the application:
:::java
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.*;
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.servlet.*;
public class HelloWorld extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
resp.getWriter().print("Hello from Java!\n");
}
public static void main(String[] args) throws Exception{
Server server = new Server(Integer.valueOf(System.getenv("PORT")));
ServletContextHandler context = new ServletContextHandler(ServletContextHandler.SESSIONS);
context.setContextPath("/");
server.setHandler(context);
context.addServlet(new ServletHolder(new HelloWorld()),"/*");
server.start();
server.join();
}
}
Cedar recognizes Java apps by the existence of a pom.xml file. Here's an example pom.xml for the Java/Jetty app we created above. The maven-appassembler-plugin generates an execution wrapper with the correct CLASSPATH.
:::xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.example</groupId>
<version>1.0-SNAPSHOT</version>
<artifactId>helloworld</artifactId>
<dependencies>
<dependency>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-servlet</artifactId>
<version>7.4.5.v20110725</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>servlet-api</artifactId>
<version>2.5</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>appassembler-maven-plugin</artifactId>
<version>1.1.1</version>
<executions>
<execution>
<phase>package</phase>
<goals><goal>assemble</goal></goals>
<configuration>
<assembleDirectory>target</assembleDirectory>
<programs>
<program>
<mainClass>HelloWorld</mainClass>
<name>webapp</name>
</program>
</programs>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
Prevent build artifacts from going into revision control by creating this file:
:::term
target
Build your app locally:
:::term
$ mvn install
To run your web process, you need to declare what command to use. We'll use Procfile to declare how our web process type is run. The appassembler plugin takes care of generating a run script, target/bin/webapp, which we'll use to start the web app.
Here's what the Procfile looks like:
:::term
web: sh target/bin/webapp
Now that you have a Procfile, you can start your application with Foreman:
:::term
$ foreman start
15:52:23 web.1 | started with pid 21416
15:52:24 web.1 | 2011-08-18 15:52:24.066:INFO::jetty-7.4.5.v20110725
15:52:24 web.1 | 2011-08-18 15:52:24.142:INFO::started o.e.j.s.ServletContextHandler{/,null}
15:52:24 web.1 | 2011-08-18 15:52:24.168:INFO::Started SelectChannelConnector@0.0.0.0:5000 START
Your app will come up on port 5000. Test that it's working with curl or a web browser, then Ctrl-C to exit.
We now have the three major components of our app: build configuration and dependencies in pom.xml, process types in Procfile, and our application source in src/main/java/HelloWorld.java. Let's put it into Git:
:::term
$ git init
$ git add .
$ git commit -m "init"
Create the app on the Cedar stack:
:::term
$ heroku create --stack cedar
Creating stark-sword-398... done, stack is cedar
http://stark-sword-398.herokuapp.com/ | git@heroku.com:stark-sword-398.git
Git remote heroku added
Deploy your code:
:::term
$ git push heroku master
Counting objects: 9, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (5/5), done.
Writing objects: 100% (9/9), 1.37 KiB, done.
Total 9 (delta 0), reused 0 (delta 0)
-----> Heroku receiving push
-----> Java app detected
-----> Installing Maven 3.0.3..... done
-----> executing .maven/bin/mvn -B -Duser.home=/tmp/build_1cq2vqzdjg7yh -DskipTests=true clean install
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building helloworld 1.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
...
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 25.671s
[INFO] Finished at: Thu Aug 18 05:22:18 UTC 2011
[INFO] Final Memory: 10M/225M
[INFO] ------------------------------------------------------------------------
-----> Discovering process types
Procfile declares types -> web
-----> Compiled slug size is 12.4MB
-----> Launching... done, v5
http://stark-sword-398.herokuapp.com deployed to Heroku
Now, let's check the state of the app's processes:
:::term
$ heroku ps
Process State Command
------------ ------------------ ------------------------------
web.1 up for 10s sh target/bin/webapp
The web process is up. Review the logs for more information:
:::term
$ heroku logs
...
2011-08-18T05:30:55+00:00 heroku[web.1]: Starting process with command `java -Xmx384m -Xss256k -XX:+UseCompressedOops -classpath target/classes:"target/dependency/*" HelloWorld`
2011-08-18T05:30:56+00:00 app[web.1]: 2011-08-18 05:30:56.310:INFO::jetty-7.4.5.v20110725
2011-08-18T05:30:56+00:00 app[web.1]: 2011-08-18 05:30:56.353:INFO::started o.e.j.s.ServletContextHandler{/,null}
2011-08-18T05:30:56+00:00 app[web.1]: 2011-08-18 05:30:56.389:INFO::Started SelectChannelConnector@0.0.0.0:22464 STARTING
2011-08-18T05:30:56+00:00 heroku[web.1]: State changed from starting to up
Looks good. We can now visit the app with heroku open.
The Spring MVC Hibernate tutorial will guide you through setting up a database-driven application on Heroku.